1. Field of the Invention
The invention relates to an arrangement with at least one superconductive cable and a first cryostat surrounding the superconductive cable for conducting a first cooling agent therethrough, wherein the cryostat is composed of at least one thermally insulated pipe, and wherein the cryostat encloses a hollow space over its entire length in which the cable is arranged and through which the first cooling agent is conducted during operation of the arrangement (EP 2 234 122 B1).
2. Description of Related Art
A superconductive cable includes electrical conductors of a material which changes over into the superconductive state at sufficiently low temperatures. The electrical direct current resistance of a correspondingly constructed conductor is zero with sufficient cooling as long as a certain current, the critical current, is not exceeded. Suitable materials are, for example oxidic materials on the basis of rare earths (ReBCO), particularly YBCO (yttrium-barium-copper oxide), or BSCCO (bismuth-strontium-calcium-copper oxide). Sufficiently low temperatures for bringing such a material into the superconductive state are, for example, between 67K and 110K. Suitable cooling agents are for example, nitrogen, helium, neon and hydrogen or mixtures of these materials. Since the stated temperatures are significantly above the absolute zero point of −273.16° C.=0K, conductors of corresponding materials are called high temperature superconductors (HTS). This is also true for other superconductive materials such as, for example magnesium diboride which change over into the superconductive state at temperatures of about 39K or lower which are also significantly above 0K.
EP 2 234 122 B1 mentioned in the beginning discloses an arrangement in which a superconductive cable is arranged in a cryostat. The cryostat consists of two pipes of metal arranged concentrically and at a distance from each other, wherein the pipes enclose between each other a thermal insulation constructed as vacuum insulation. The oxidic materials already mentioned above are used as superconductive materials on the basis of rare earths. For example for cooling the cable, liquid nitrogen is used which can be kept at a sufficiently low cooling temperature over a longer period of time with a conventional vacuum insulated cryostat. Liquid nitrogen cannot be used for lower temperatures which are below 63K because it changes into a solid state at these temperatures. In addition, for a cooling agent which is at a correspondingly cool temperature, it is more difficult to keep the cooling agent cool, over a longer period of time.